1. Field of the Invention
The present invention relates to a method for manufacturing a mold of a light guide plate, and more particularly, to a method for manufacturing a mold of a light guide plate with a plurality of microstructures thereon.
2. Description of the Prior Art
Backlight units are known in the art. The backlight module, which is a key element in the liquid crystal displays (LCDs), is widely used in monitors, notebooks, digital cameras, projectors and so on. The light guide plate is one of the important parts of the backlight module. The light guide plate is capable of guiding light emitted from a light source so as to transform a point light source or a linear light source into a planar light source.
The methods of manufacturing the light guide plates are typically divided into two major categories: printing process and non-printing process. The non-printing process has advantages of stable quality, high precision, and so on, and is a mainstream manufacturing method of the light guide plates in the market. The non-printing process is to form patterns on a mold first and to manufacture the light guide plates by the mold with an injection molding process.
The methods of manufacturing the mold of the light guide plates are typically divided into two major categories. One is forming patterns on the mold directly with an etching process. The other is forming patterns on the mold with a semiconducting process, such as a photolithography process. For example, U.S. Pat. No. 5,776,636 discloses related technology. Please refer to FIG. 1 to FIG. 6 which are diagrams of manufacturing a mold of a light guide plate in the prior art. As shown in FIG. 1, a photoresist layer 11 is spread upon a substrate 10 first. The substrate 10 can be a glass substrate. As shown in FIG. 2 and FIG. 3, a photomask 12 with specified pattern thereon is utilized for forming a photoresist pattern on the substrate 10 with exposing and developing processes. As shown in FIG. 4, a metal layer 13 is plated upon the photoresist pattern with a sputtering process or an evaporation process. As shown in FIG. 5, a metal plate 14 is electroformed on the metal layer 13. As shown in FIG. 6, the metal layer 13 is separated from the photoresist layer 11 and the substrate 10 so as to generate a mold 15 with a pattern on the surface corresponding to the photoresist pattern.
However the conventional method of manufacturing the mold of the light guide plates has disadvantages as follows. A height of the pattern on the mold depends on a thickness of the photoresist layer 11, which causes difficulty in controlling the height of the pattern on the mold. In addition, the pattern on the mold is limited due to a small range of the thickness of the photoresist layer 11. Furthermore, the pattern on the mold is formed with exposing and developing processes so that microstructures or complicated structures can not be formed on the pattern.